For implementation of a file copy function or a file migration function offered by a host computer (server), conventionally, the host computer itself reads and writes data from and to a storage apparatus. This places a high load on a central processing unit (CPU) of the host computer and/or incurs a high communication load between the host computer and the storage apparatus.
In view of the above, some techniques have been proposed which reduce a load applied when the host computer reads and writes data from and to the storage apparatus.
Japanese Laid-open Patent Publication No. 2006-53737
Japanese Laid-open Patent Publication No. 2006-236019
Japanese Laid-open Patent Publication No. 2008-250695
On the other hand, there is a technique, called an offloaded data transfer (ODX) function, of reducing the CPU load of the host computer and the communication load between the host computer and the storage apparatus. The offloaded data transfer function enables loads associated with file copy and migration operations of the host computer to be transferred (offloaded) to the storage apparatus.
Therefore, supporting the offloaded data transfer function facilitates a reduction in the CPU load of the host computer and the communication load between the host computer and the storage apparatus. However, the storage apparatus may take on an excessive load from the host computer, and thus simply supporting the offloaded data transfer function does not always provide efficient copy control on the whole.